The present invention relates to the liquid transport of solid material and involves the technology of mass exchanging processes between solid and liquid phases, such as cleaning, leaching and dissolving. The invention may be used in radiochemical, chemical, hydrometallurgical and another branches of industry. The invention may provide an efficient process for the treatment of a solid material, having the form of a cylindrical block whose length is 3 to 5 times its width and having a considerable density and a mass up to tens of grammes. The treatment may be, for example, cleaning metal goods by removing fatty contaminations or leaching of material pieces.
The most advanced mass-exchanging process involves a counter-current motion of a solid and a liquid phase. Such a process makes it possible to cut down the contact time of the solid and liquid phases sufficient for effective mass-exchange. However, there is insufficient average time of the solid phase in the apparatus. The residence time is mainly dependent on the rate of solid phase settling and connected with the accumulation of that solid phase in the lower portion of the apparatus under a liquid (as it takes place in the case of column apparatus). This circumstance has led to the development of complicated and, as a rule, unreliable units for solid phase discharging.
The upward motion of the solid pieces simplifies their discharging and makes it possible to vary their residence time in mass-exchanging apparatus within a wider range and moreover by simpler apparatus.
A method for transporting solid material pieces on an inclined surface up to the top of a mass-exchanging apparatus under vibroexciter influence was described in the USSR Authors Certificate No 648240, wherein solid material pieces are disposed on the inclined surface which is oscillated at an angle to the direction of movement of the solid material.
This method allows the possibility of a counter-current motion of liquid and solid phases but the existence of moving parts exposed to the aggressive processing environment makes the method highly difficult for performing under large scale conditions. Furthermore, it is difficult to ensure reliable connection of inlet and outlet pipes with apparatus which is undergoing such oscillating movement. It is obvious that the vibrating source must have a limited mass to create the oscillations as vibration increases sharply with increasing exciter mass. As a result the apparatus must have small dimensions and consequently it has a low throughput.
A pulsed transporter and a method for transporting discrete solid objects during a mass-exchanging process with counter-current motion of solid and liquid phases are known from EP 0358354A. This apparatus comprises a generally V-shaped duct, adapted to contain a liquid and having an inlet for receiving at its upper end objects to be transported and an outlet for discharging treated objects. The outlet is connected to the inlet by a base below the inlet opening. Means are provided for applying at intervals a pressure pulse to the liquid for displacing objects through a discharge duct. Transport of the objects is the result of liquid pulsation and the difference in the solid properties in the inlet and outlet of the duct.
Simplicity of the transporter design and absence of moving structural components are important advantages. However it is desirable to arrange a plurality of such transporters in series with each other to provide a residence period of solid in the liquid sufficient for efficient mass-exchanging between the liquid and the solid material pieces which have considerable mass and density. As a result the reliability of equipment is decreased and the size of the technological plant is enlarged.
Method and apparatus for transporting a solid phase in a liquid using pneumatic pulse power are known from USSR ac N 874093. In this method liquid reciprocation created under the action of saw-like pulses. The motive force (the high-speed pressure of the liquid during its movement under the actions of the pneumatic pulse) overcomes the resistant force due to gravity, friction of the solid against the apparatus walls and local losses. As a result the solid material displaces upward and counter-currently to the liquid stream. The apparatus comprises a: V-shaped duct, adapted to contain the liquid phase; a inlet for receiving the object to be transported and, connected with a pulse generator, and a solid outlet.
Simplicity of the apparatus design and absence of moving components exposed to solid pieces or processing liquid are advantages. However, the method is not efficient at causing transport of the solid objects, having considerable mass and density, as the solid pieces motion is stoped when settling velocity of the pieces becomes the same as the lifting velocity.
The present invention provides a method for improving a counter-current mass-exchange in a xe2x80x9csolid-liquidxe2x80x9d system and an apparatus for transporting solid material pieces in the liquid during the mass-exchanging process.
According to one aspect of the present invention there is provided a method for improving a counter-current mass-exchange in a xe2x80x9csolid-liquidxe2x80x9d system the method comprising forming pneumatic pulses in the apparats, convering said pulses into reciprocal motion of the liquid phase by applying the pulses to the liquid phase and movement of the solid material pieces upwardly along a sloping ramp characterised in that the reciprocal motion of the liquid phase is directed via slits in the ramp at an acute angle to the direction of the movement of the solid material pieces upwardly along the ramp.
Preferably the reciprocal motion of the liquid phase is directed via slits in the ramp at an acute angle to the ramp causing reciprocal motion of the solid material pieces upwardly away from and along the ramp and downwardly towards the ramp so that the solid material pieces are transported upwardly along the ramp.
Preferably the slits are formed within steps in the ramp, whereby the steps limit movement of the solid material pieces downwardly along the ramp.
Preferably the pneumatic pulses have a sawtooth shed gas pressure profile.
Preferably said liquid reciprocation is directed in the form of a flat jets at ad acute angle.
The flat jets are preferably divided into fluid inlet/outlet zones distributed along the length of the apparatus.
Preferably said flat jets are directed upwardly and inclined at an acute angle to said solid pieces motion direction during a pressure pulse phase.
In a particular embodiment of the method said flat jets are formed simultaneously over substantially the entire length of the apparatus.
In another embodiment of the method said flat jets are formed in adjacent zones in counter-phase mode.
In yet another particular embodiment of the method said flat jets are formed in a running wave manner.
According to another aspect of the present invention there is provided an apparatus for transporting solid material pieces in a liquid phase during mass-exchanging processes comprising: means for forming pneumatic pulses; means for converting said pulses into reciprocal motion of the liquid phase by applying the pulses to the liquid phase and movement of the solid material pieces upwardly along a sloping ramp characterised in that the reciprocal motion of the liquid phase is directed via slits in the ramp at an acute angle to Me direction of the movement of the solid meal pieces upwardly along the ramp.
Preferably, the reciprocal motion of the liquid phase is directed via slits in the ramp at an acute angle to the ramp causing reciprocal motion of the solid material pieces away from and along the amp and downwardly towards the ramp so that the solid material pieces are transported upwardly along the ramp.
Preferably, the slits are formed avid steps in the ramp, whereby the steps limit movement of the solid material pieces downwardly along the ramp.
Preferably, the pneumatic pulses have a sawtooth shaped gas pressure profile.
Preferably, the apparatus comprises a tubular vessel, a ramp arranged inside the vessel an inlet and an outlet v charging and discharging respectively materials to and from the vessel and a pulse chamber for causing reciprocal motion of the liquid.
Preferably the longitudinal axis of the vessel is disposed at an angle of from 5 to 60xc2x0 to the horizontal.
Preferably the ramp is in the form of a plurality of flat vanes arranged along the lien of the vessel.
Preferably said flat vanes form slotted nozzles.
Preferably said slotted nozzles are provided by a sleeve, disposed across said nozzles.
Preferably, the flat vanes are at an angle of from 5 to 450 to the longitudinal axis of the vessel, the vanes defining upper and lower areas of the vessel.
Preferably said lower area is divided by transverse partitions into zones, each of which is connected via a pipe to a pulse chamber.
Preferably, a grid is located between adjacent vanes of the ramp.